The long-term objectives of these ongoing projects are: (1) to culture postimplantation embryos in order to determine the hormone and growth factor requirements for normal development as well as to understand the mechanisms of abnormal development induced by various teratogens including the glucocorticoids; (2) to further develop and refine our short-term screening assay for potential teratogens using the human embryonic palatal mesenchyme cells in culture; (3) to develop culture conditions which will sustain the growth and differentiation of palatal epithelial cells; (4) to understand the mechanisms at a biochemical level by which glucocorticoids and TCDD induce cleft palate and affect differentiation of the palatal epithelial and mesenchymal cells in culture; and (5) to define hormonal regulation of alpha-fetoprotein and metallothionein gene expression in the embryo.